The present invention relates to a two-dimensional position/orientation measuring mark, a method and an apparatus for measuring a two-dimensional position/orientation, a control apparatus for an image recording apparatus, and also a control apparatus for a manipulator. More specifically, the present invention is directed to a measuring mark, a measuring method and a measuring apparatus, and an image recording apparatus utilizing these mark, measuring method and apparatus, and also a control apparatus for controlling a manipulator, in which position/orientation can be two-dimensionally measured in a simple manner and at low cost, an easy handily operation can be achieved, and measurement precision does not depend upon speeds of a mark formed medium.
Very recently, in combination with complex works and high-leveled words by robot, strong demands are made to measure two-dimensional positions and orientations in high precision at high speed. For instance, when an object is gripped by a manipulator and a gripped object is located at a proper place, a position and an orientation of this object must be measured in high precision and at high speed.
As the conventional two-dimensional position/orientation measuring apparatus, there is such a measuring apparatus with employment of imaging means such as a television camera as an outer field sensor in order to perform the visual feedback control. In accordance with this two-dimensional position/orientation measuring apparatus, an object under measurement is imaged by the imaging means such as the television camera to thereby produce information about the position/orientation of the object under measurement. Then, the position and orientation obtained from this information are converted into the coordinate values of the coordinate system fixed to the external environment, and both the position and the orientation of the object under measurement are measured in response to a difference between the target coordinate values of this coordinate system and the detected coordinate values obtained from the coordinate conversion.
However, according to this two-dimensional position/orientation measuring apparatus, the two-dimensional sensor such as a CCD is employed as the imaging means of the television camera, and thus the one-frame-data acquisition speed is 1/30 seconds or 1/60 seconds. In general, this data acquisition speed is very slow, as compared with the feedback cycle time of the motor control apparatus for the manipulator, namely less than 1/1000 seconds. Since the pixel quantity of one frame is about 500.times.500, sufficient resolution cannot be expected. Moreover, since the information amount to be processed becomes large, the exclusively used data processing circuits are required to increase the processing speed, resulting in high cost.
As either the two-dimensional position/orientation measuring apparatus or the two-dimensional position measuring apparatus for solving these problems, there are shown the measuring apparatuses as disclosed in, for instance, the Unexamined Japanese Patent Application Publication Nos. Hei. 3-17503, and Sho. 64-18001.
In the two-dimensional position/orientation measuring apparatus indicated in the Unexamined Japanese Patent Application Publication No. Hei. 3-17503, the one-dimensional optical sensor is arranged on each of the four edges of the regular square. These one-dimensional optical sensors read out the grid-shaped separating lines formed on the semiconductor wafer, and then the position and the orientation of the semiconductor wafer are measured based upon the light reception level distributions of two pairs of one-dimensional optical sensors arranged on the respective opposite edges, and the difference between these light reception level distributions.
Also, in the two-dimensional position measuring apparatus described in the Unexamined Japanese Patent Application Publication No. Sho. 64-18001, a point source such as a small bulb is mounted on the object under measurement. The light originated from this point source is collected by way of the light collecting optical system, the collected light beam is splitted by the beam splitter, and the splitted light beams are detected by the one-dimensional sensors along two directions perpendicular to each other. Then, the sensor signal is inputted into the corresponding position detecting circuit to thereby measure the position of the object under measurement.
On the other hand, the Unexamined Japanese Patent Application Publication No. Hei. 6-118735 discloses the control apparatus for the image recording apparatus for detecting the error in the registration of the plural color images formed on the recording medium of the image recording apparatus. This control apparatus for the image recording apparatus is comprised of the first and second mark detectors arranged on the first and second edges of the chevron shaped pattern, and the calculating circuit for inputting therein the mark detection timing signals outputted from the first and second mark detectors to perform a predetermined calculation, whereby the registration error in the plural color images is detected based upon this calculation result. In this control apparatus for the image recording apparatus, the first mark in which two edges of the chevron shaped pattern are made in the first color, the second mark in which two edges of the chevron shaped pattern are made in the second color, and the third mark in which the first edge of the chevron shaped pattern is made in the first color and also the second edge thereof is made in the second color are formed at each of the predetermined timing. The first to third marks are detected by the first and second mark detectors by transporting the recording medium. When the first and second mark detectors detect the first to third marks, these mark detectors output the detection timing signals to the calculating circuit. The calculating circuit enters the detection timing signal therein to execute a predetermined calculation, and detects the registration errors in the first and second color images based on this calculation result. The image recording apparatus controls the registration of the color image based on the detected errors.
However, in accordance with the two-dimensional position/orientation measuring apparatus described in the Unexamined Japanese Patent Application Publication No. Hei. 3-17503, since the one-dimensional optical sensors are arranged on the respective edges of the regular square, at least four sets of one-dimensional optical sensors are required, resulting in high manufacturing cost. On the other hand, according to the two-dimensional position measuring apparatus disclosed in the Unexamined Japanese Patent Application Publication No. Sho. 64-18001, since a large number of optical components involving the imaging lens, the corn-shaped lens, and the beam splitter are required, the measuring apparatus would become complex, resulting in high manufacturing cost. Also, since the point source such as the small bulb is needed, a special care should be taken in order to avoid damages thereof. Furthermore, according to the color registration error detecting apparatus as described in the Unexamined Japanese Patent Application Publication No. Hei. 6-118735, the mark detection timing signal is substituted for the formula while the speed of the recording medium is constant so as to detect the color registration errors. As a result, when a variation is made in the speed of the recording medium, the resultant detection precision would be lowered.